Eucalyptus oil is used commonly as a decongestant and expectorant for upper respiratory tract infections or inflammations, as well as for various musculoskeletal conditions. The oil is found in numerous over-the-counter cough and cold lozenges as well as in inhalation vapors or topical ointments. Veterinarians use the oil topically for its reported antimicrobial activity. Other applications include as an aromatic in soaps or perfumes, as flavoring in foodstuffs or beverages, and as a dental or industrial solvent. High quality scientific evidence is currently lacking.

Eucalyptus oil contains 70-85% 1,8-cineole (eucalyptol), which is also present in other plant oils. Eucalyptol is used as an ingredient in some mouthwash and dental preparations, as an endodontic solvent, and may possess antimicrobial properties. Listerine® mouthrinse is a combination of essential oils (eucalyptol, menthol, thymol, methyl salicylate) that has been shown to be efficacious for the reduction of dental plaque and gingivitis.

Topical use or inhalation of eucalyptus oil at low concentrations may be safe, although significant and potentially lethal toxicity has been consistently reported with oral use and may occur with inhalation use as well. All routes of administration should be avoided in children.

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

GRADE *

Aromatherapy using eucalyptus has been studied for its effects on pain, depression, and feelings of satisfaction in life in arthritis patients. Aromatherapy may help reduce pain and depression, but does not appear to alter the feeling of satisfaction in life. Additional study is needed to clarify these findings.

C

Further research is needed to confirm anti-inflammatory and mucolytic activity before this agent can be recommended in upper and lower airway diseases.

C

Although commonly used in non-prescription products, there is inconclusive scientific study of eucalyptus oil or eucalyptol. Better research is necessary before a recommendation can be made.

C

Although studies on combination mouthwashes show effectiveness (such as Listerine®), it is not clear that eucalyptus oil by itself is effective or safe for this purpose.

C

Effectiveness of eucalyptus oil applied to the skin for headache relief has not been supported with reliable human research.

C

Limited evidence suggests that eucalyptus essential oil may be beneficial for patients with skin ulcers when combined with antibiotics. More studies are needed to confirm these early findings.

C

Nicobrevin is a proprietary product marketed as an aid for smoking cessation that contains quinine, menthyl valerate, camphor, and eucalyptus oil. Despite use of this product, there is a lack of evidence suggesting benefit of this product or eucalyptus oil for smoking cessation.

C

Preliminary research shows that Citriodiol® spray, containing eucalyptus, may reduce the number of tick bites and thereby tick-borne infections, although additional studies are warranted.

C

* Key to grades

A: Strong scientific evidence for this useB: Good scientific evidence for this useC: Unclear scientific evidence for this useD: Fair scientific evidence for this use (it may not work)F: Strong scientific evidence against this use (it likley does not work)

Tradition / Theory
The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

Application of 5% to 20% in an oil-based formulation or 5% to 10% in an alcohol-based formulation has been used. In one study, topical lemon eucalyptus extract spray (Citriodiol®) was applied daily for two weeks to the lower extremities to reduce tick attachment.

Eucalyptus oil should be taken with caution, since small amounts of oil taken by mouth have resulted in severe and deadly reactions. For eucalyptus oil, doses of 0.05 to 0.2 milliliter or 0.3 to 0.6 gram daily have been used traditionally, but may cause toxic side effects. For infusions prepared with eucalyptus leaf, a quantity of 2 to 3 grams of eucalyptus leaf in 150 milliliters of water, three times a day, has been used traditionally, but may result in toxic side effects.

Tincture with 5% to 10% eucalyptus oil or a few drops placed into a vaporizer as an inhalant have been used.

Eucalyptol (1,8-cineole) is a major chemical in eucalyptus oil, and it is used in some commercially sold mouthwashes.

Children (younger than 18 years)

Severe side effects have been reported in children after small doses of eucalyptus have been taken by mouth or applied to the skin. Eucalyptus is not recommended for use by infants and young children, especially near the face and nose.

Safety
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Case reports describe allergic rash after exposure to eucalyptus oil, either alone or as an ingredient in creams. One child developed a rash after taking eucalyptus oil by mouth. Reports also describe hives after exposure to eucalyptus pollen.

An herbal survey in asthmatic patients found 12% of asthmatic patients using eucalyptus. Ironically, eucalyptus may cause allergic reactions and the exacerbation of asthma. Worsening of rhinoconjunctivitis and vocal cord dysfunction within minutes of exposure to eucalyptus has been reported.

Side Effects and Warnings

Severe and potentially deadly side effects are reported with the use of eucalyptus oil by mouth in children and adults. These include slowing of the brain and central nervous system, drowsiness, seizures, and coma. Use caution if driving or operating heavy machinery. Anecdotal reports suggest that serious side effects can develop with as little as one teaspoon taken by mouth. Reports also suggest that inhaled eucalyptus products or bathtub exposure can cause symptoms. Avoid eucalyptus products in infants and young children, as reports describe severe reactions after exposure by mouth or by application to the skin. Ingestion by children of vaporizer formulas containing eucalyptus has been reported.

Symptoms reported with eucalyptus oil taken by mouth include abdominal pain, nausea, vomiting, diarrhea, dizziness, muscle weakness, constricted pupils, a feeling of suffocation or difficulty breathing, wheezing, cough, blue discoloration of the lips or skin, delirium, or convulsions. Drowsiness, hyperactivity, difficulty walking, muscle weakness, slurred speech, fever, pneumonia, and headache have also been reported. Case reports describe several abnormalities in heart function after eucalyptus oil is taken by mouth, including abnormal rhythms, loss of heartbeat, low blood pressure, and complete disruption of the heart and circulation. Individuals with seizure disorders, heart disease, disorders of the stomach or intestines, or lung disease should use caution.

Published reports describe "attacks" in patients with acute intermittent porphyria (AIP), an inherited disorder affecting the liver and blood. Individuals with AIP should avoid eucalyptus products. Other case reports mention symptoms in individuals who have kidney or liver disease or who are taking other medications that are processed by the liver. Eucalyptus is reported to lower blood sugar in diabetic animals, although reliable human studies are not available in this area. Nonetheless, caution is advised in patients with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Serum glucose levels may need to be monitored by a healthcare provider, and medication adjustments may be necessary.

A strain of bacteria found on eucalyptus may cause infection. Worsening of asthma and rhinoconjunctivitis has been reported.

Cardiovascular collapse and multi-organ failure has been reported following a massive ingestion of mouthwash containing phenolic compounds (eucalyptol, menthol, thymol).

Pregnancy and Breastfeeding

Due to the known side effects of eucalyptus, and the unknown effects during pregnancy or breastfeeding, eucalyptus should be avoided by pregnant and breastfeeding women.

Multiple case reports associate eucalyptus oil taken by mouth with slowing of the mind and nervous system. These symptoms may be worsened when eucalyptus is taken with sedating medications. Examples include benzodiazepines such as lorazepam (Ativan®) or diazepam (Valium®), barbiturates such as phenobarbital or pentobarbital, narcotics such as codeine, some antidepressants, and alcohol. Caution is advised while driving or operating machinery. Eucalyptus may also interact with amphetamine.

Eucalyptus should be taken with caution if combined with medications that lower blood sugar. Patients taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare provider. Medication adjustments may be necessary.

Several components of eucalyptus interfere with the way the body processes certain drugs using the liver's "cytochrome P450" enzyme system. As a result, the levels of these drugs may be decreased in the blood with reduced intended effects. Patients using any medications should check the package insert and speak with a healthcare provider or pharmacist about possible interactions.

When applied to the skin with 5-fluorouracil lotion (5-FU, Efudex®, Carac®), eucalyptus may increase the absorption of 5-FU.

Many tinctures contain high levels of alcohol and may cause nausea or vomiting when taken with metronidazole (Flagyl®) or disulfiram (Antabuse®).

Interactions with Herbs and Dietary Supplements

Eucalyptus may increase the drowsiness caused by some herbs or supplements, such as German chamomile or lemon balm. Caution is advised while driving or operating machinery.

Eucalyptus may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.

Eucalyptus may interfere with the way the body processes certain herbs or supplements using the liver's "cytochrome P450" enzyme system. As a result, the levels of other herbs or supplements may become too low in the blood. In addition, levels of eucalyptus in the body may be affected by herbs or supplements that affect the P450 system, such as bloodroot, cat's claw, or chamomile.

Eucalyptus has been said to worsen the side effects of borage, coltsfoot, comfrey, hound's tooth, or Senecio species, although there is no reliable research in this area.

The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.